Zoom lens, imaging device and information device

ABSTRACT

A zoom lens includes, in order from an object side in an optical axis a first lens group having a positive refractive power, a second lens group having a negative refractive power; a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a positive refractive power, and an aperture stop arranged between the third lens group and the fourth lens group, an interval between the first lens group and the second lens group being increased, an interval between the second lens group and the third lens group being varied, an interval between the third lens group and the fourth lens group being decreased, and an interval between the fourth lens group and the fifth lens group being decreased when changing a magnification from a wide-angle end to a telephoto end.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/482,401 filed May 29, 2012, which is based on and claims priorityfrom Japanese Patent Application No. 2011-121122 filed May 30, 2011,Japanese Patent Application No. 2011-149582 filed Jul. 5, 2011, andJapanese Patent Application No. 2011-182948 filed Aug. 24, 2011, thedisclosures of each of which are hereby incorporated by reference intheir entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to a zoom lens for use in a video camera,electronic still camera or the like using an imaging element, an imagingdevice and information device having such a zoom lens.

The zoom lens of this invention can be used as an imaging zoom lens inan imaging device such as a silver salt camera, digital still camera,video camera, or digital video camera. The information device of thisinvention can be used as a digital still camera, portable digitalassistant or the like.

2. Description of the Related Art

In recent years, a zoom lens has generally been used in photographingoptical systems for use in digital still cameras or the like. A zoomlens including an approximate 50 mm field angle in a focal length rangein 35 mm conversion is especially known.

With respect to these zoom lenses, users strongly request downsizing,wide angle, and high-speed auto focusing (hereinafter, referred to asAF).

Various positive lead type zoom lenses including in order from an objectside to an image side a first lens group having a positive refractivepower, a second lens group having a negative refractive power and asubsequent group are conventionally known (refer to Patent Document 1:Japanese Patent Application Publication No. H03-228008, Patent Document2: Japanese Patent Publication No. 3716418, Patent Document 3: JapanesePatent Publication No. 3397686, Patent Document 4: Japanese PatentPublication No. 4401451 and Patent Document 5: Japanese PatentApplication Publication No. 2010-175954). Such a zoom lens can easilyincrease a magnification ratio and downsize an entire length with apositive lead type lens.

Each of the zoom lenses described in Patent Documents 1-5 includes aninner focus type lens. The zoom lens described in Patent Document 1performs focusing by the movement of the second lens group. Each of thezoom lenses described in Patent Documents 2-5 performs focusing by themovement of the third lens group.

In the zoom lens described in Patent Document 1, which performs focusingby the movement of the second lens group, the sizes of a motor and anactuator are likely to be increased, and the maximum diameter of a lensbarrel is also likely to be increased because of a large weight of thesecond lens group.

Such a zoom lens has a problem in high-speed AF and quiescence inanimation photographing because the second lens group has a largeweight.

Each of the zoom lenses described in Patent Documents 2-5 performsfocusing by the third lens group having a negative refractive power.

However, it is difficult to significantly reduce a weight of thefocusing group of the zoom lens in each of Patent Documents 2-4. In thezoom lens described in Patent Document 5, the third lens group forfocusing is constituted by one negative lens, so that the weight of thefocusing group is reduced; thus, high-speed AF and a small diameter lensbarrel can be accomplished. However, it is considered that theperformance of the third lens group should be further improved and thezoom lens should be further downsized.

In recent years in which a zoom lens has mainly been used, high-speed AFis required as described above. It is necessary for a zoom lens toreduce an entire length of lenses (a distance from a lens surface on themost object side to an image side) when using a zoom lens in order todownsize the zoom lens.

It is also necessary to downsize a focusing lens for increasing an AFspeed.

Moreover, considering the application of a zoom lens to a high-enddigital camera, it is necessary to have resolution corresponding to animaging element having at least 10 million pixels over the entirezooming area.

A zoom lens which is suitable for a high magnification ratio includes inorder from the object side to the image side a first lens group having apositive refractive power, a second lens group having a negativerefractive power, a third lens group having a negative refractive power,a fourth lens group having a positive refractive power and a fifth lensgroup having a positive refractive power.

Such a conventional zoom lens including a five-group constitution ofpositive, negative, negative, positive, positive is described in PatentDocument 6 (Japanese Patent Application Publication H10-48518) andPatent Document 7 (Japanese Patent Application Publication 2000-28923).

The zoom lens described in Patent Document 6 includes a five-groupconstitution of positive, negative, negative, positive, positive in aspecific example, and performs focusing by moving a third lens group asa focusing group. However, the third lens group is large and heavybecause the third lens group is a cemented lens made of negative andpositive lenses. For this reason, a load for moving the focusing groupis increased and a size of a motor or the like for driving the focusinggroup and a time for focusing are also increased.

The zoom lens described in Patent Document 7 includes a five-groupconstitution of positive, negative, negative, positive, positive inEmbodiment 4, and performs focusing by moving the third lens group as afocusing group. However, the third lens group is large and heavy becausethe third lens group includes three lenses of negative, positive andnegative. For this reason, a load for moving the focusing group isincreased and a size of a motor or the like for driving the focusinggroup and a time for focusing are also increased similar to PatentDocument 6.

SUMMARY

The present invention has been made in view of the above circumstances.An object of the present invention is to provide a zoom lens which issuitable as a zoom lens for a compact and high performance digitalcamera, and can accomplish high-speed AF, a downsized driving system forAF and resolution corresponding to an imaging element having over 10million pixels, an imaging device and an information device using such azoom lens.

In order to achieve the above object, one embodiment of the presentinvention provides a zoom lens comprising, in order from an object sidein an optical axis: a first lens group having a positive refractivepower; a second lens group having a negative refractive power; a thirdlens group having a negative refractive power; a fourth lens grouphaving a positive refractive power; a fifth lens group having a positiverefractive power; and an aperture stop arranged between the third lensgroup and the fourth lens group, an interval between the first lensgroup and the second lens group being increased, an interval between thesecond lens group and the third lens group being increased, an intervalbetween the third lens group and the fourth lens group being decreased,and an interval between the fourth lens group and the fifth lens groupbeing decreased when changing a magnification from a wide-angle end to atelephoto end, the third lens group including one negative lens made ofa negative meniscus lens having a concave surface on the object side,and focusing being performed by moving the third lens group in anoptical axis direction, wherein a curvature radius of an object sidesurface of the third lens group, R31, a curvature radius of an imageside surface of the third lens group, R32, a focal length of the thirdlens group, F3, a synthesis focal length of the second and third lensgroups at the wide-angle end, F23w, a synthesis focal length of thesecond and third lens groups at the telephoto end, F23t, a focal lengthat the wide-angle end, Fw, a focal length at the telephoto end, Ft, and√(Fw×Ft), Fm satisfy the following conditions (1), (2), (3).1.0<(R31−R32)/|F23w|<10.0  (1)1.0<(R31−R32)/|F23t|<10.0  (2)1.4<|F3|/Fm<2.5  (3)

One embodiment of the present invention also provides a zoom lenscomprising, in order from an object side to an image side in an opticalaxis: a first lens group having a positive refractive power; a secondlens group having a negative refractive power; a third lens group havinga negative refractive power; a fourth lens group having a positiverefractive power; a fifth lens group having a positive refractive power;and an aperture stop arranged between the third lens group and thefourth lens group, an interval between the first lens group and thesecond lens group being increased, an interval between the second lensgroup and the third lens group being varied, an interval between thethird lens group and the fourth lens group being decreased, and aninterval between the fourth lens group and the fifth lens group beingdecreased when changing a magnification from a wide-angle end to atelephoto end, and focusing being performed by moving the third lensgroup, wherein a focal length of the third lens group, f3, a focallength of an entire system at the wide-angle end, fw, a focal length ofthe entire system at the telephoto end, ft satisfy the followingcondition (7).1.4<|f3/√{square root over ( )}(fw×ft)|<3  (7)

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide further understandingof the invention, and are incorporated in and constitute a part of thisspecification. The drawings illustrate embodiments of the invention and,together with the specification, serve to explain the principle of theinvention.

FIG. 1 is a view illustrating a zoom lens in Embodiment 1.

FIG. 2 shows aberration diagrams of the zoom lens in Embodiment 1 at thewide-angle end.

FIG. 3 shows aberration diagrams of the zoom lens in Embodiment 1 at theintermediate focal length.

FIG. 4 shows aberration diagrams of the zoom lens in Embodiment 1 at thetelephoto end.

FIG. 5 is a view illustrating a zoom lens in Embodiment 2.

FIG. 6 shows aberration diagrams of the zoom lens in Embodiment 2 at thewide-angle end.

FIG. 7 shows aberration diagrams of the zoom lens in Embodiment 2 at theintermediate focal length.

FIG. 8 shows aberration diagrams of the zoom lens in Embodiment 2 at thetelephoto end.

FIG. 9 is a view illustrating a zoom lens in Embodiment 3.

FIG. 10 shows aberration diagrams of the zoom lens in Embodiment 3 atthe wide-angle end.

FIG. 11 shows aberration diagrams of the zoom lens in Embodiment 3 atthe intermediate focal length.

FIG. 12 shows aberration diagrams of the zoom lens in Embodiment 3 atthe telephoto end.

FIG. 13 is a view illustrating a zoom lens in Embodiment 4.

FIG. 14 shows aberration diagrams of the zoom lens in Embodiment 4 atthe wide-angle end.

FIG. 15 shows aberration diagrams of the zoom lens in Embodiment 4 atthe intermediate focal length.

FIG. 16 shows aberration diagrams of the zoom lens in Embodiment 4 atthe telephoto end.

FIG. 17 is a view illustrating a zoom lens in Embodiment 5.

FIG. 18 shows aberration diagrams of the zoom lens in Embodiment 5 atthe wide-angle end.

FIG. 19 shows aberration diagrams of the zoom lens in Embodiment 5 atthe intermediate focal length.

FIG. 20 shows aberration diagrams of the zoom lens in Embodiment 5 atthe telephoto end.

FIG. 21 is a view illustrating a zoom lens in Embodiment 6.

FIG. 22 shows aberration diagrams of the zoom lens in Embodiment 6 atthe wide-angle end.

FIG. 23 shows aberration diagrams of the zoom lens in Embodiment 6 atthe intermediate focal length.

FIG. 24 shows aberration diagrams of the zoom lens in Embodiment 6 atthe telephoto end.

FIG. 25 is a view illustrating a zoom lens in Embodiment 7.

FIG. 26 shows aberration diagrams of the zoom lens in Embodiment 7 atthe wide-angle end.

FIG. 27 shows aberration diagrams of the zoom lens in Embodiment 7 atthe intermediate focal length.

FIG. 28 shows aberration diagrams of the zoom lens in Embodiment 7 atthe telephoto end.

FIG. 29 is a view illustrating a zoom lens in Embodiment 8.

FIG. 30 shows aberration diagrams of the zoom lens in Embodiment 8 atthe wide-angle end.

FIG. 31 shows aberration diagrams of the zoom lens in Embodiment 8 atthe intermediate focal length.

FIG. 32 shows aberration diagrams of the zoom lens in Embodiment 8 atthe telephoto end.

FIG. 33A, 33B, 33C are views each illustrating an embodiment of aninformation device.

FIG. 34 is a view illustrating a system configuration of the device inFIGS. 33A-33C, 36.

FIG. 35 is a graph illustrating a range prescribed by conditions (8),(9). In the graph, the horizontal axis is an Abbe's number (νd3) ind-line and the vertical axis is a partial dispersion ratio (θg, F).

FIG. 36 is a perspective view schematically illustrating an externalconstitution of a digital camera as an imaging device according to anembodiment of the present invention as seen from a subject side.

FIG. 37 is a perspective view schematically illustrating an externalappearance of the digital camera in FIG. 36 as seen from aphotographer's side.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be hereinafter described.

A zoom lens according to one embodiment of the present inventionincludes in order from an object side to an image side a first lensgroup having a positive refractive power, a second lens group having anegative refractive power, a third lens group having a negativerefractive power, a fourth lens group having a positive refractivepower, a fifth lens group having a positive refractive power and anaperture stop between the fourth and fifth lens groups. In such a zoomlens, the interval between the first and second lens groups isincreased, the interval between the second and third lens groups isincreased, the interval between the third and fourth lens groups isdecreased and the interval between the fourth and fifth lens groups isdecreased when changing a magnification from the wide-angle end to thetelephoto end. The zoom lens has the following features.

More specifically, the third lens group is constituted by one negativelens, and this negative lens is a negative meniscus lens having aconcave surface on the object side. The focusing is performed by themovement of the third lens group in the optical axis direction.

A curvature radius of an object side surface of the third lens group,R31, a curvature radius of an image side surface of the third lensgroup, R32, a focal length of the third lens group, F3, a synthesisfocal length of the second and third lens groups at the wide-angle end,F23w, a synthesis focal length of the second and third lens groups atthe telephoto end, F23t, and a focal length at the wide-angle end, Fw, afocal length at the telephoto end, Ft, and √/(Fw×Ft), Fm satisfy thefollowing conditions (1), (2), (3).1.0<(R31−R32)/|F23w|<10.0  (1)1.0<(R31−R32)/|F23t|<10.0  (2)1.4<|F3|/Fm<2.5  (3)

It is preferable for a maximum image height, Y′ and the focal length atthe wide-angle end, Fw in the zoom lens to satisfy the followingcondition (5).0.75<Y′/Fw  (5)

It is preferable for the focal length at the telephoto end, Ft and thefocal length at the wide-angle end, Fw in the zoom lens to satisfy thefollowing condition (6).2.8<Ft/Fw  (6)

It is preferable for an Abbe's number of a material of one negative lensconstituting the third lens group, νd in the zoom lens to satisfy thefollowing condition (4).ν/d>50  (4)

A material outside the range of the condition (4) can be used as amaterial for the above one negative lens.

An information device of one embodiment of the present inventionincludes the above-described zoom lens as an optical system forphotographing. A silver salt camera, video camera or the like can beused as such an information device.

The information device includes a photographing function in which anobject image by a zoom lens is formed on a light-receiving surface ofthe imaging element, and can be used as a digital still camera, videocamera or the like.

The information device can be constituted as a portable digitalassistant.

The zoom lens includes an inner focus type which performs focusing bythe movement of the third lens group. The third lens group as thefocusing group is constituted by one negative lens. The zoom lens isconstituted to satisfy the conditions (1)-(3).

The focusing group is light because it includes one lens, so that highspeed AF, a reduced lens barrel diameter and silent focusing can beaccomplished.

However, it is necessary to preferably control eccentric errorsensitivity of the third lens group because the third lens group is afocusing lens group which frequently moves for the focusing operation.It is disadvantage in the downsizing of the third lens group if thepower of the third lens group is reduced for controlling the eccentricerror sensitivity.

Each of the conditions (1), (2) is a condition which defines anappropriate range of a power balance of each surface of the one negativelens constituting the third lens group.

If the parameters exceed the ranges of the conditions (1), (2), load toeach surface is increased, aberrations are generated, and the eccentricerror sensitivity is also increased.

The numerators of the parameters of the conditions (1), (2) are positivevalues, respectively. Therefore, the one negative lens constituting thethird lens group is a negative meniscus lens having a concave surface onthe object side.

The condition (3) is a condition which defines an appropriate range of afocal length of the third lens group, F3. Fm of the denominator of theparameter is √(Fw×Ft), and the geometric average of the focal lengths atthe wide-angle end and the telephoto end is given.

The decrease in the parameter, |F3|/Fm means the decrease in the focallength of the third lens group and the increase in the negative power ofthe third lens group. This is advantageous in downsizing, but if theparameter exceeds the lower limit value of the condition (3), theeccentric error sensitivity of the third lens group is increased, whichis a disadvantage in terms of processing performance.

If the parameter exceeds the upper limit value of the condition (3), thenegative power of the third lens group is reduced. This is advantageousin terms of processing performance, but is disadvantageous indownsizing.

By simultaneously satisfying the conditions (1), (2), (3), a focusinggroup, which is suitable for downsizing, has small eccentric errorsensitivity and controls generation of aberrations, can be accomplishedby one lens.

It is more preferable for each of the parameters of the conditions(1)-(3) to satisfy the following conditions (1A), (2A), (3A).1.5<(R31−R32)/|F23w|<9.5  (1A)1.5<(R31−R32)/|F23t|<9.5  (2A)1.5<|F3|/Fm<2.3  (3A)

The zoom lens of this embodiment includes the above-described five-groupconstitution. The first to third lens groups constitute a front groupand the fourth and fifth lens groups constitute a back group. The backgroup is made up of two lens groups, so that the load of the front groupfor changing a magnification is reduced, and the design freedom can beimproved. Therefore, it is advantageous in terms of aberrationcorrection and a processing performance.

When changing a magnification, all of the lens groups move to contributeto the change in a magnification, so that the load for changing amagnification is dispersed to each group to be reduced. This isadvantageous in terms of aberration correction and a processingperformance. It becomes possible to effectively reduce the movementamount of the first lens group when changing a magnification.Accordingly, it is also advantageous in terms of downsizing.

The condition (5) is a condition which controls a field angle and canachieve a half field angle of 36.8° or more at the wide-angle end.

It is more preferable for the parameter of the condition (5) to satisfythe following condition (5A).0.87<Y′/Fw  (5A)

The condition (6) is a condition which controls a zoom ratio and canachieve a magnification ratio of 2.8 times or more.

It is more preferable for the zoom ratio to satisfy the followingcondition (6A).2.8<Ft/Fw<5  (6A)

By constituting the third lens group with a material which satisfies thecondition (4), a higher performance can be achieved.

More specifically, the generation of various chromatic aberrations canbe controlled by using a relatively low dispersion glass for the lensconstituting the third lens group because the third lens group isconstituted by one lens. With this constitution, the aberrations can befurther effectively corrected by reducing the load of other lens groups.

The mechanism can be simplified if the opening diameter of the aperturestop is set constant regardless of a magnification, but the change in Fnumber can be decreased by increasing the opening diameter of thetelephoto end compared to the opening diameter of the wide-angle end.

The diameter of the aperture stop can be reduced when the decrease inthe light volume which reaches an image surface is required. However, itis preferable to reduce the light volume by inserting an ND filter orthe like without significantly changing the diameter of the aperturestop because the decrease in resolution due to a diffraction phenomenoncan be prevented.

Eight embodiments of the zoom lenses are sequentially described,referring to FIGS. 1, 5, 9, 13, 17, 21, 25, 29. These embodimentscorrespond to the after-described Embodiments 1-8.

The same reference numbers are used for respective figures in order toavoid complication.

Referring to FIGS. 1, 5, 9, 13, 17, 21, 25, 29, the left side is anobject side and the right side is an image surface side.

The zoom lens includes in order from the object side in the optical axisa first lens group I having a positive refractive power, a second lensgroup II having a negative refractive power, a third lens group IIIhaving a negative refractive power, a fourth lens group IV having apositive refractive power, a fifth lens group V having a positiverefractive power and an aperture stop S between the third lens group IIIand the fourth lens group IV.

In each figure, the top view illustrates the lens arrangement at thewide-angle end, the middle view illustrates the lens arrangement at theintermediate focal length and the bottom view illustrates the lensarrangement at the telephoto end. The arrows illustrate movement ofrespective lens groups when changing a magnification from the wide-angleend to the telephoto end.

As is apparent from each figure, in the zoom lens of the presentinvention, all of the lens groups move when changing a magnificationfrom the wide-angle end to the telephoto end.

Namely, the interval between the first lens group I and the second lensgroup II is increased, the interval between the second lens group II andthe third lens group III is increased, the interval between the thirdlens group III and the fourth lens group IV is decreased, and theinterval between the fourth lens group IV and the fifth lens group V isdecreased. The aperture stop S moves together with the fourth lens groupIV when changing a magnification.

The third lens group III is constituted by one negative lens. Thisnegative lens is a negative meniscus lens having a concave surface onthe object side. The focusing is performed by the movement of the thirdlens group III in the optical axis direction.

Reference number F on the right side of the figure illustrates twotransparent parallel plates.

In a camera using an imaging element such as a CCD or CMOS, for example,a digital still camera, a low pass filter, infrared cut glass or thelike is provided close to the light-receiving surface of the imagingelement. The light-receiving surface of the imaging element is protectedby a cover glass.

The transparent parallel plates are various filters such as a low passfilter, and are plates virtually substituted by two transparent parallelplates optically equivalent to cover glasses.

The constitution of each lens group in the zoom lens illustrating anembodiment in FIG. 1 is as follows.

The first lens group I is a cemented lens including in order from theobject side a negative meniscus lens having a convex surface on theobject side and a positive meniscus lens having a convex surface on theobject side.

The second lens group II includes in order from the object side anegative meniscus lens having a convex surface on the object side, abiconcave lens having an aspheric surface on both surfaces, and abiconvex lens.

The third lens group III is one negative meniscus lens having a strongconcave surface on the object side.

The fourth lens group IV includes in order from the object side abiconvex lens having an aspheric surface on both surfaces and a strongconvex surface on the object side and a cemented lens of a biconvex lensand a biconcave lens.

The fifth lens group V includes in order from the object side a biconvexlens having an aspheric surface on both surfaces and a negative meniscuslens having a convex surface on the object side.

The constitution of each lens group in the zoom lens illustrating anembodiment in FIG. 5 is as follows.

The first lens group I is a cemented lens including in order from theobject side a negative meniscus lens having a convex surface on theobject side and a positive meniscus lens having a convex surface on theobject side.

The second lens group II includes in order from the object side anegative meniscus lens having a convex surface on the object side, abiconcave lens having an aspheric surface on both surfaces and abiconvex lens.

The third lens group III includes one negative meniscus lens having astrong concave surface on the object side.

The fourth lens group IV includes in order from the object side abiconvex lens having an aspheric surface on both surfaces and a strongconvex surface on the object side and a cemented lens having a biconvexlens and a biconcave lens.

The fifth lens group V includes a biconvex lens having an asphericsurface on both surfaces and a negative meniscus lens having a convexsurface on the object side.

The constitution of each lens group in the zoom lens illustrating anembodiment in FIG. 9 is as follows.

The first lens group I is a cemented lens including in order from theobject side a negative meniscus lens having a convex surface on theobject side and a positive meniscus lens having a convex surface on theobject side.

The second lens group II includes in order from the object side anegative meniscus lens having a convex surface on the object side, abiconcave lens having an aspheric surface on both surfaces and abiconvex lens.

The third lens group III includes one negative meniscus lens having astrong concave surface on the object side.

The fourth lens group IV includes in order from the object side abiconvex lens having an aspheric surface on both surfaces and a strongconvex surface on the object side and a cemented lens having a biconvexlens and a biconcave lens.

The fifth lens group V includes in order from the object side a biconvexlens having an aspheric surface on both surfaces and a negative meniscuslens having a convex surface on the object side.

The constitution of each lens group in the zoom lens illustrating anembodiment in FIG. 13 is as follows.

The first lens group I is a cemented lens including in order from anobject side a negative meniscus lens having a convex surface on theobject side and a positive meniscus lens having a convex surface on theobject side.

The second lens group II includes in order from the object side anegative meniscus lens having a convex surface on the object side, abiconcave lens having an aspheric surface on both surfaces and abiconvex lens.

The third lens group III includes one negative meniscus lens having astrong concave surface on the object side.

The fourth lens group IV includes in order from the object side abiconvex lens having an aspheric surface on both surfaces and a strongconvex surface on the object side and a cemented lens of a biconvex lensand a biconcave lens.

The fifth lens group V includes in order from the object side a biconvexlens having an aspheric surface on both surfaces and a negative meniscuslens having a convex surface on the object side.

The constitution of each lens group in the zoom lens illustrating anembodiment in FIG. 17 is as follows.

The first lens group I is a cemented lens including in order from theobject side a negative meniscus lens having a convex surface on theobject side and a positive meniscus lens having a convex surface on theobject side.

The second lens group II includes in order from the object side anegative meniscus lens having a convex surface on the object side, abiconcave lens having an aspheric surface on both surfaces and abiconvex lens.

The third lens group II includes one negative meniscus lens having astrong concave surface on the object side.

The fourth lens group IV includes in order from the object side abiconvex lens having an aspheric surface on both surfaces and a strongconvex surface on the object side and a cemented lens of a biconvex lensand a biconcave lens.

The fifth lens group V includes in order from the object side a biconvexlens having an aspheric surface on both surfaces and a negative meniscuslens having a convex surface on the object side.

The constitution of each lens group in the zoom lens illustrating anembodiment in FIG. 21 is as follows.

The first lens group I is a cemented lens including in order from theobject side a negative meniscus lens having a convex surface on theobject side and a positive meniscus lens having a convex surface on theobject side.

The second lens group II includes in order from the object side anegative meniscus lens having a convex surface on the object side, abiconcave lens having an aspheric surface on both surfaces and abiconvex lens.

The third lens group III includes one negative meniscus lens having astrong concave surface on the object side.

The fourth lens group IV includes in order from the object side abiconvex lens having an aspheric surface on both surfaces and a strongconvex surface on the object side and a cemented lens of a biconvex lensand a biconcave lens.

The fifth lens group V includes in order from the object side a biconvexlens having an aspheric surface on both surfaces and a negative meniscuslens having a convex surface on the object side.

The constitution of each lens group in the zoom lens illustrating anembodiment in FIG. 25 is as follows.

The first lens group I is a cemented lens including in order from theobject side a negative meniscus lens having a convex surface on theobject side and a positive meniscus lens having a convex surface on theobject side.

The second lens group II includes in order from the object side anegative meniscus lens having a convex surface on the object side, abiconcave lens having an aspheric surface on both surfaces and abiconvex lens.

The third lens group III includes one negative meniscus lens having astrong concave surface on the object side.

The fourth lens group IV includes in order from the object side abiconvex lens having an aspheric surface on both surfaces and a strongconvex surface on the object side and a cemented lens having a biconvexlens and a biconcave lens.

The fifth lens group V includes in order from the object side a biconvexlens having an aspheric surface on both surfaces and a negative meniscuslens having a convex surface on the object side.

The constitution of each lens group in the zoom lens illustrating anembodiment in FIG. 29 is as follows.

The first lens group I is a cemented lens including in order from theobject side a negative meniscus lens having a convex surface on theobject side and a positive meniscus lens having a convex surface on theobject side.

The second lens group II includes in order from an object side anegative meniscus lens having a convex surface on the object side, abiconcave lens having an aspheric surface on both surfaces and abiconvex lens.

The third lens group III includes one negative meniscus lens having astrong concave surface on the object side.

The fourth lens group IV includes in order from the object side abiconvex lens having an aspheric surface on both surfaces and a strongconvex surface on the object side and a cemented lens of a biconvex lensand a biconcave lens.

The fifth lens group V includes in order from the object side a biconvexlens having an aspheric surface on both surfaces and a strong convexsurface on the image side and a negative meniscus lens having a convexsurface on the object side.

An embodiment of an information device will be described with referenceto FIGS. 33A-34.

FIGS. 33A-33C illustrate external appearances of a camera device (cameraportion of information device), and FIG. 34 illustrates a systemconstitution of the information device.

As illustrated in FIG. 34, the information device 30 includes aphotographing lens 31, a light-receiving element 45 (imaging element inwhich 5-10 million pixels are two-dimensionally arranged) and a finder33. The information device 30 is configured to read an image of aphotographing object formed by the photographing lens 31 with thelight-receiving element 45.

The above-described imaging lens, particularly, an imaging lensdescribed in each of the following embodiments 1-8 is used as thephotographing lens 31.

The output from the light-receiving element 45 is processed by a signalprocessor 42 which is controlled by a central processing unit 40, and isconverted into digital information. The digitalized image information isprocessed in an image processor 41 which is controlled by the centralprocessing unit 40, and is recorded in a semiconductor memory 44.

A liquid crystal monitor 39 can display an image in photographingprocessed in the image processor 41, and can display an image recordedin the semiconductor memory 44. The image recorded in the semiconductormemory 44 can be sent outside with a communication card 43 or the like.

The image processor 41 includes a function which electrically correctsshading, a function which trims an image central portion, and the like.

The photographing lens 31 is in a collapsed state as illustrated in FIG.33A when the information device is carried, and a lens barrel isextended as illustrated in FIG. 33B in response to a turning-onoperation with a power source switch 36 by a user.

In this case, each group of the zoom lens inside the lens barrel isarranged such that an object distance is infinity. The focusing to afinite distance is performed by half-pressing a shutter button 35. Thezooming is performed in response to the operation of a zooming adjuster34, and the finder 33 changes a magnification according to the zoomingoperation.

The focusing operation is performed by moving the third lens group asdescribed above.

The operation button 37 as illustrated in FIG. 33C is used whendisplaying an image recorded in the semiconductor memory 44 on theliquid crystal monitor 38 and sending the image outside by using acommunication card or the like. The semiconductor memory, thecommunication card or the like is used by inserting in a dedicated orgeneralized socket 39A, 39B.

It is not always necessary for each lens group to be arranged on theoptical axis when the photographing lens 31 is in a collapsed state. Thethickness of the information device can be further reduced if the firstand second lens groups are retracted from the optical axis to be housedin parallel with another lens group, for example.

As described above, the imaging lens descried in each of Embodiments 1-8can be used as the photographing lens 31 in the information devicehaving a camera device as a photographing section, and a small and highquality information device including a camera function with thelight-receiving element 45 having over 5-10 million pixels can beachieved.

Hereinafter, embodiments of a zoom lens, imaging device and informationdevice will be described with reference to the drawings.

Embodiments of the present invention will be described before describingspecific embodiments. In this case, FIGS. 1, 5, 9, 13, 17, 21 and 25correspond to the first to seventh embodiments, but can be also used asthe following Embodiments 1-7.

A zoom lens according to the embodiment of the present inventionincludes in order from the object side to the image side a first lensgroup I having a positive refractive power, a second lens group IIhaving a negative refractive power, a third lens group III having anegative refractive power, a fourth lens group IV having a positiverefractive power, a fifth lens group V having a positive refractivepower and an aperture stop S arranged between the third and fourth lensgroups III, IV. All of the lens groups moves, the interval between thefirst and second lens groups I, II is increased, the interval betweenthe second and third lens groups II, III is varied, the interval betweenthe third and fourth lens groups III, IV is decreased, the intervalbetween the fourth and fifth lens groups IV, V is decreased, and theaperture stop S moves together with the fourth lens group IV accordingto an embodiment when changing a magnification from a telephoto end to awide-angle end.

The first lens group I includes in order from the object side to theimage side a first lens L1 made of a negative meniscus lens having aconvex surface on the object side and a second lens L2 made of apositive meniscus lens having a convex surface on the object side. Thesefirst and second lenses L1, L2 form a cemented lens in which the firstand second lenses are bonded to each other.

The second lens group II includes a third lens L3 made of a negativemeniscus lens having a convex surface on the object side, a fourth lensL4 made of a biconcave lens having an aspheric surface on both surfacesand a strong concave surface on the image side and a fifth lens L5 madeof a biconvex lens having a strong convex surface on the object side.

The third lens group III includes a six lens L6 made of a negativemeniscus lens having a convex surface on the image side.

The fourth lens group IV includes a seventh lens L7 made of a biconvexlens having an aspheric surface on both surfaces and a strong convexsurface on the object side, an eighth lens L8 made of a biconvex lenshaving a strong convex surface on the image side and a ninth lens L9made of a biconcave lens having a strong concave surface on the objectside. The eighth and ninth lenses L8, L9 are bonded to form a cementedlens.

The fifth lens group IV includes a tenth lens L10 made of a biconvexlens having an aspheric surface on both surfaces and a strong convexsurface on the object side and an eleventh lens L11 made of a negativemeniscus lens having a convex surface on the object side.

The above zoom lens includes the following various features.

The following condition (7) is satisfied where a focal length of thethird lens group is f3, a focal length of the entire system at thewide-angle end is fw, a focal length of the entire system at thetelephoto end is ft and an intermediate focal length Fm of the focallength fw and the focal distance ft is Fm=√fw×ft.1.4<|f3/√{square root over ( )}(fw×ft)|<3  (7)

The condition (7) expresses a ratio of the intermediate focal length andthe focal length of the third lens group. If the parameter exceeds theupper limit value of 3, the displacement of the third lens group havinga focusing function is increased in close photographing, so that theinterval between the second and third lens groups has to be increased,resulting in the increase in the entire length of the optical system. Ifthe parameter is below the lower limit value of 1.4, the focal length ofthe third lens group becomes too short, and the displacement from theinfinity to the shortest photographing distance in the focusing isreduced. However, the sensitivity is increased, and an accuratepositional accuracy of the third lens group is required, resulting inthe complication of the mechanical constitution.

The following condition (8) is satisfied where the focal length of thefirst lens group is f1 and the focal length of the second lens group isf2.2.2<|f1/f2|<3.5  (8)

The condition (8) expresses a ratio of the focal lengths of the firstand second lens groups. If the parameter exceeds the upper limit valueof 3.5, the focal length of the second lens group becomes too short, sothat deterioration in aberrations when changing a magnification isincreased. Manufacturing error sensitivity is also increased, causing aproblem in a production performance. If the parameter is below the lowerlimit value of 2.2, the focal length of the second lens group becomestoo long, so that the displacement of the second lens group whenchanging a magnification is increased, resulting in the increase in theentire length of the optical system.

The following condition (9) is satisfied where the focal length of thefirst lens group is f1, the focal length of the entire system at thewide-angle end is fw, the focal length of the entire system at thetelephoto end is ft, and the intermediate focal length of the focallength fw and the focal length ft is Fm=Fm=√fw×ft.2.2<|f1/√{square root over ( )}(fw×ft)|<3.5  (9)

The condition (9) expresses a ratio of the focal length of the firstlens group and the intermediate focal length. If the parameter exceedsthe upper limit value of 3.5, the focal length of the first lens groupbecomes too long, so that the displacement of the first lens group whenchanging a magnification is increased, resulting in the increase in theentire length of the optical system.

The focal length of the first lens group becomes too short if theparameter is below the lower limit value of 2.2, and deterioration inaberrations when changing a magnification is increased. Manufacturingerror sensitivity and a manufacturing cost are also increased, causing aproblem in a production performance.

The following condition (10) is satisfied where the focal length of thesecond lens group is 12 and the focal length of the third lens group isf3.0.2<f2/f3<0.9  (10)

The condition (10) expresses a ratio of the focal lengths of the secondand third lens groups. If the parameter exceeds the upper limit value of0.9, the displacement of the second lens group having a function forchanging a magnification is increased when changing a magnification, sothat the entire length of the optical system is increased. Deteriorationin aberrations in focusing is also increased because the focal length ofthe third lens group of the focusing group becomes too short. If theparameter is below the lower limit value of 0.2, deterioration inaberrations when changing a magnification is increased because the focallength of the second lens group becomes too short. Manufacturing errorsensitivity is also increased, causing a problem in a productionperformance. Moreover, the focal length of the third lens group of thefocusing group becomes too long, so that the displacement for focusingis increased, resulting in the increase in the entire length of theoptical system.

The following conditions (11), (12) are satisfied where an Abbe's numberrelative to d-line of the negative lens of the third lens group is νd3,and a partial dispersion ratio of the negative lens of the third lensgroup is θg, F=(ng−nF)/(nF−nC) where a refractive index relative tog-line is ng, a refractive index relative to F-line is nF, and arefractive index relative to c-line is nC.νd3>50  (11)θg,F<1.2×10−3·νd3+0.62  (12)

The condition (11) expresses an Abbe's number in d-line of the negativelens constituting the third lens group. The condition (12) expresses apartial dispersion ratio of the negative lens of the third lens group.

FIG. 35 illustrates an area defined by the conditions (11), (12). InFIG. 35, the horizontal axis is νd and the vertical axis is θg, F. Thedeterioration in aberrations due to the focusing can be controlled byusing a glass material within an area in which θg, F is in the lowerside of the condition (12). A group having a negative power as a wholeby combining a positive lens made of a glass material having largedispersion and a negative lens made of a glass material having smalldispersion is generally used for a group having a negative power inorder to control a chromatic aberration. However, even if the third lensgroup is constituted by one negative lens, a chromatic aberration can bepreferably corrected over the entire zooming area, and the deteriorationin aberrations due to the focusing can be controlled by using the glassmaterial within the above range.

The third lens group having a focusing function is constituted by onenegative lens. By satisfying the above conditions (7), (11), (12), aproblem regarding the deterioration in aberrations due to the focusingcan be solved even if the third lens group of the focusing group isconstituted by one negative lens. With this constitution, the focusinggroup can be downsized and the AF speed can be increased.

In this zoom lens, the fourth lens group and the aperture stop movetogether when changing a magnification. Therefore, the number ofcomponents can be reduced and the lens barrel unit can be downsizedbecause it is not necessary to additionally provide a driver for theaperture stop.

In this zoom lens, the fifth lens group includes at least one positivelens and one negative lens.

The above zoom lens can be used for an imaging device and an informationdevice as an optical system for photographing. As illustrated in FIG. 1,in each embodiment, the parallel plate F disposed on the image side ofthe fifth lens group IV is constituted of transparent parallel platesequivalent to various filters such as an optical low pass filter orinfrared cut filter, a cover glass (sealing glass) of a light receivingelement such as a CCD sensor, or the like.

In addition, a reference number FP illustrates an imaging surface of thezoom lens.

EMBODIMENT

Hereinafter, eight specific embodiments will be described.

The meanings of marks in Embodiments are as follows.

f: focal length of entire system

F: F-number

ω: half-field angle (deg)

surface number: number of surface (lens surface, aperture stop surface,filter, light receiving surface) counted from object side

R: curvature radius (paraxial curvature radius in aspheric surface)

D: surface interval

Nd: refractive index

νd: Abbe's number

K: conical constant of aspheric surface

A4: fourth order aspheric surface coefficient

A6: sixth order aspheric surface coefficient

A8: eighth order aspheric surface coefficient

A10: tenth order aspheric surface coefficient

A12: twelfth order aspheric surface coefficient

A14: fourteenth order aspheric surface coefficient

An aspheric surface shape is defined by the following known Equation 1by using an inverse of a paraxial curvature radius (paraxial curvature),C, a height from an optical axis, H, and a conical constant and anaspheric coefficient of each order, K, where X is an aspheric surfaceamount in an optical axis direction.X=CH ²/[1+√{square root over ( )}{1−(1+K)C ² H ² }]+A4·H ⁴ +A6·H ⁶ A8·H⁸ +A10·H ¹⁰ +A12·H ¹² +A14·H ¹⁴

The shape is specified by applying a paraxial curvature radius, aconical constant and aspheric surface coefficients.

Embodiment 1

Embodiment 1 is the zoom lens illustrated in FIG. 1.

f = 16.146~53.852   F = 3.59~5.93   ω = 42.8~14.5 SURFACE NUMBER R D Ndνd 1 35.22784 1.30000 1.84666 23.7800 2 25.43981 5.58108 1.69680 55.53003 161.95730 VARIABLE A 4 66.68463 0.97007 2.00100 29.1300 5 10.930006.31830 6 −29.18377 0.80000 1.69350 53.1800 7 26.19043 0.09955 825.80601 4.24896 1.84666 23.7800 9 −27.63060 VARIABLE B 10 −20.241670.80000 1.60300 65.4400 (S-PHM53) 11 −50.23484 VARIABLE C 12 ∞ 1.45001(APERTURE STOP) 13 15.31467 3.43574 1.51633 64.0600 14 −38.17926 0.1000015 21.44923 3.93180 1.53172 48.8400 16 −17.87906 1.45000 1.83400 37.160017 19.58694 VARIABLE D 18 19.29863 4.94809 1.58913 61.1500 19 −19.586740.23493 20 48.01352 0.80173 1.90366 31.3200 21 16.49362 VARIABLE E 22 ∞0.70000 1.53770 66.6000 23 ∞ 1.50000 24 ∞ 0.70000 1.50000 64.0000 25 ∞

The aspheric surface data is as follows.

Sixth Surface

K=0

A4=−1.12571E-05

A6=1.21899E-07

A8=2.76874E-09

A10=−4.5160E-11

A12=1.38009E-13

Seventh Surface

K=0

A4=−4.98762E-05

A6=3.02710E-07

A8=−1.83352E-09

A10=−4.9553E-12

Thirteenth Surface

K=0

A4=−2.23034E-05

A6=−3.30061E-08

A8=1.96596E-09

A10=−4.33079E-11

Fourteenth Surface

K=0

A4=−6.86789E-06

A6=1.59127E-07

A8=−8.05125E-10

A10=−2.46291E-11

Eighteenth Surface

K=−4.76959

A4=−2.06414E-06

A6=−1.71695E-07

A8=−2.33143E-09

A10=6.08643E-12

Nineteenth Surface

K=0.25043

A4=3.72591E-05

A6=−4.11291E-08

A8=−2.02648E-09

A10=3.86766E-12

In the above aspheric surface data, “E-n” denotes “10-^(n)”. This is thesame as in the following embodiments.

The glass material of the lens of the third lens group is S-PHM53manufactured by OHARA Co., Ltd.

νd and θg, F of S-PHM53 are as follows according to the publishedcatalogue.

νd=65.44

θg, F=0.5401

The variable amount data is illustrated in Table 1.

TABLE 1 FOCAL LENGTH 16.146 29.487 53.852 VARIABLE A 0.43999 6.0651116.38637 VARIABLE B 2.90306 3.44128 4.32097 VARIABLE C 17.67216 7.914752.59996 VARIABLE D 5.29575 2.75180 1.65000 VARIABLE E 27.52876 40.7082854.51902

FIGS. 2, 3, 4 are the aberration diagrams at the wide-angle end,intermediate focal length and telephoto end, respectively. The dashedline in the spherical aberration diagram illustrates a sine condition,the solid line in the astigmatism diagram illustrates a sagittal and thedashed line in the astigmatism diagram illustrates a meridional. Inaddition, “g” and “d” illustrate g-line and d-line, respectively. Theseare the same as the following other aberration diagrams.

Embodiment 2

FIG. 2 is the zoom lens illustrated in FIG. 5.

f = 16.146~53.851  F = 3.6~5.77  ω = 42.87~14.47 SURFACE NUMBER R D Ndνd 1 43.11718 1.29999 1.84666 23.78 2 31.73933 5.57706 1.69680 55.53 3190.09719 VARIABLE A 4 55.24695 0.97008 2.00100 29.13 5 10.53158 7.007586 −37.69153 0.80000 1.69350 53.18 7 39.79764 0.12000 8 35.75261 4.227721.84666 23.78 9 −27.02142 VARIABLE B 10 −22.16816 0.80000 1.60300 65.44(S-PHM53) 11 −68.86241 VARIABLE C 12 ∞ (APERTURE STOP) 1.45020 1317.70983 4.99510 1.51633 64.06 14 −25.76032 0.10000 15 24.82196 3.731811.53172 48.84 16 −18.83887 1.44999 1.83400 37.16 17 19.93203 VARIABLE D18 18.95445 5.30000 1.58913 61.15 19 −22.79198 0.10000 20 46.106500.80000 1.90366 31.32 21 16.80062 VARIABLE E 22 ∞ 0.70000 1.53770 66.6023 ∞ 1.50000 24 ∞ 0.70000 1.50000 64.00 25 ∞

The aspheric surface data is as follows.

Sixth Surface

K=0

A4=−6.13912E-05

A6=6.02764E-07

A8=−3.68927E-09

A10=−5.86282E-12

Seventh Surface

K=0

A4=−9.55771E-05

A6=6.67024E-07

A8=−5.78157E-09

A10=3.44512E-12

Thirteenth Surface

K=0

A4=−2.21195E-05

A6=−1.07672E-06

A8=1.98544E-08

A10=−3.47093E-10

Fourteenth Surface

K=0

A4=5.12674E-06

A6=−9.94310E-07

A8=1.53589E-08

A10=−2.78900E-10

Eighteenth Surface

K=−1.2879

A4=−1.57778E-05

A6=−7.80973E-08

A8=−8.69905E-10

A10=3.89552E-12

Nineteenth Surface

K=0.98584

A4=4.43195E-05

A6=5.66872E-08

A8=−2.64609E-09

A10=1.33387E-11

The glass material of the lens of the third lens group is S-PHM53manufactured by OHARA Co., Ltd.

νd and θg, F of S-PHM53 are as follows according to the publishedcatalogue.

νd=65.44

θg, F=0.5401

The variable amount data is illustrated in Table 2.

TABLE 2 FOCAL LENGTH 16.14596 29.48643 53.85135 VARIABLE A 0.440128.55784 22.14102 VARIABLE B 3.74070 3.93725 4.34529 VARIABLE C 18.456978.08099 2.59987 VARIABLE D 5.92655 3.05743 1.65001 VARIABLE E 28.2998541.24833 54.53266

FIGS. 6, 7, 8 are the aberration diagrams at the wide-angle end,intermediate distance, telephoto end in Embodiment 2, respectively.

Embodiment 3

Embodiment 3 is the zoom lens illustrated in FIG. 9

f = 16.146~53.85  F = 3.62~5.67  ω = 42.8~14.46 SURFACE NUMBER R D Nd νd1 44.83622 1.30000 1.84666 23.78 2 30.32788 5.80250 1.77250 49.60 3152.20233 VARIABLE A 4 55.56877 0.97009 2.00100 29.13 5 10.85110 6.679026 −40.92454 0.80000 1.77703 47.4 (LLAH87) 7 36.32245 0.65885 8 30.897324.44422 1.84666 23.78 9 −26.99833 VARIABLE B 10 −24.45877 0.800001.64850 53.02 (S-BSM71) 11 −103.58339 VARIABLE C 12 ∞ (APERTURE STOP)1.45008 13 16.52481 5.35383 1.51633 64.06 14 −25.99633 0.10000 1523.78029 3.61747 1.51742 52.43 16 −22.01894 1.45000 1.83400 37.16 1717.55937 VARIABLE D 18 19.88520 5.30000 1.58913 61.15 19 −22.744380.10000 20 53.58387 0.80000 1.90366 31.32 21 18.67841 VARIABLE E 22 ∞0.70000 1.53770 66.60 23 ∞ 1.50000 24 ∞ 0.70000 1.50000 64.00 25 ∞

The aspheric surface data is as follows.

Sixth Surface

K=0

A4=−8.18151E-06

A6=−2.01833E-07

A8=2.53333E-09

A10=−1.29107E-11

Seventh Surface

K=0

A4=−3.23283E-05

A6=−1.88341E-07

A8=1.96755E-09

A10=−1.43273E-11

Thirteenth Surface

K=0

A4=−3.22004E-05

A6=−9.60992E-07

A8=1.55589E-08

A10=−2.82657E-10

Fourteenth Surface

K=0

A4=3.53815E-06

A6=−8.66214E-07

A8=1.17377E-08

A10=−2.24402E-10

Eighteenth Surface

K=−1.27337

A4=−1.58768E-05

A6=−1.86624E-07

A8=6.94712E-10

A10=−5.97184E-12

Nineteenth Surface

K=0

A4=3.31640E-05

A6=−1.06067E-07

A8=−6.29723E-10

A10=0

The glass material of the lens of the third lens group is S-BSM71manufactured by OHARA Co., Ltd.

νd and θg, F of S-BSM71 are as follows according to the publishedcatalogue.

νd=53.02

θg, F=0.5547

The variable amount data is illustrated in Table 3.

TABLE 3 FOCAL LENGTH 16.15 29.49 53.85 VARIABLE A 0.44000 8.8725722.67111 VARIABLE B 2.87666 3.12901 4.33617 VARIABLE C 19.29016 8.437622.59994 VARIABLE D 6.18178 3.32394 1.65001 VARIABLE E 27.38221 39.6610951.81615

FIGS. 10, 11, 12 are the aberration diagrams at the wide-angle end,intermediate distance, telephoto end in Embodiment 3, respectively.

Embodiment 4

Embodiment 4 is a zoom lens illustrated in FIG. 13.

f = 16.19450~45.75015  F = 3.62882~5.85754 ω = 42.69841~16.94375 SURFACENUMBER R D Nd νd 1 33.04630 1.30000 1.84666 23.78 2 24.61909 5.030611.69680 55.53 3 136.08670 VARIABLE A 4 66.82379 0.97000 2.00100 29.13 510.13620 6.58248 6 −27.08140 0.80000 1.69350 53.18 7 42.28382 0.10000 836.12687 4.06747 1.84666 23.78 9 −23.91703 VARIABLE B 10 −19.227230.80000 1.60300 65.44 (S-PHM53) 11 −40.79376 VARIABLE C 12 ∞ (APERTURESTOP) 1.45000 13 15.53437 3.73586 1.51633 64.06 14 −28.31772 0.10000 1526.51545 3.96987 1.53172 48.84 16 −16.08335 1.45000 1.83400 37.16 1721.49926 VARIABLE D 18 18.61811 5.28649 1.58913 61.15 19 −19.326440.10000 20 50.34422 0.82401 1.90366 31.32 21 15.67976 VARIABLE E 22 ∞0.70000 1.53770 66.60 23 ∞ 1.50000 24 ∞ 0.70000 1.50000 64.00 25 ∞

The aspheric surface data is as follows

Sixth Surface

K=0

A4=−2.62797E-05

A6=2.15039E-07

A8=1.25881E-09

A10=−3.37339E-11

A12=−5.96466E-14

Seventh Surface

K=0

A4=−6.94415E-05

A6=2.98647E-07

A8=−1.81245E-09

A10=−2.26671E-11

Thirteenth Surface

K=0

A4=−1.84404E-05

A6=−9.86481E-08

A8=1.21421E-09

A10=−2.38227E-11

Fourteenth Surface

K=0

A4=9.50545E-06

A6=8.22895E-08

A8=−9.41319E-10

A10=−1.57178E-11

A12=0

Eighteenth Surface

K=−4.00213

A4=5.35275E-06

A6=−6.14576E-08

A8=−3.35757E-09

A10=3.63892E-11

Nineteenth Surface

K=−0.0203

A4=4.11207E-05

A6=6.45731E-08

A8=−4.12993E-09

A10=4.1149E-11

The glass material of the lens of the third lens group is S-BSM53manufactured by OHARA Co., Ltd.

νd and θg, F of S-BSM53 are as follows according to the publishedcatalogue.

νd=65.44

θg, F=0.5401

The variable amount data is illustrated in Table 4.

TABLE 4 FOCAL LENGTH 16.19450 27.22021 45.75015 VARIABLE A 0.440003.12474 13.64650 VARIABLE B 2.92021 3.87145 4.13333 VARIABLE C 16.991527.10888 2.60000 VARIABLE D 5.50038 2.77435 1.65000 VARIABLE E 26.5755438.89238 48.19625

FIGS. 14, 15, 16 are the aberration diagrams at the wide-angle end,intermediate distance, telephoto end in Embodiment 4, respectively.

Embodiment 5

Embodiment 5 is a zoom lens illustrated in FIG. 17.

f = 16.146~53.84  F = 3.65~5.74  ω = 41.5~14.87 SURFACE NUMBER R D Nd νd1 46.03179 1.30005 1.84666 23.78 2 31.22940 5.51888 1.77250 49.60 3152.04501 VARIABLE A 4 51.07120 0.97002 2.00100 29.13 5 10.77721 6.637096 −42.16678 0.79999 1.77030 47.40 7 38.75553 0.96368 8 30.38725 4.332031.84666 23.78 9 −29.02408 VARIABLE B 10 −21.91807 0.80000 1.64850 53.02(S-BSM71) 11 −79.56447 VARIABLE C 12 ∞ (APERTURE STOP) 1.44994 1318.62497 4.02774 1.51633 64.06 14 −25.81393 0.09995 15 20.81187 4.012711.51742 52.43 16 −19.74213 1.44999 1.83400 37.16 17 19.22015 VARIABLE D18 20.95766 5.30002 1.58913 61.15 19 −22.01066 0.10001 20 42.360600.79999 1.90366 31.32 21 16.44550 VARIABLE E 22 ∞ 0.70000 1.53770 66.6023 ∞ 1.50000 24 ∞ 0.70000 1.50000 64.00 25 ∞

The aspheric surface data is as follows

Sixth Surface

K=0

A4=5.52979E-05

A6=−1.46723E-06

A8=1.40955E-08

A10=−5.75258E-11

Seventh Surface

K=0

A4=3.02092E-05

A6=−1.53901E-06

A8=1.44769E-08

A10=−6.26901E-11

Thirteenth Surface

K=0

A4=−8.40542E-06

A6=−4.37152E-07

A8=1.03740E-08

A10=−2.45238E-10

Fourteenth Surface

K=0

A4=2.47361E-05

A6=−6.21729E-07

A8=1.37690E-08

A10=−2.72842E-10

Eighteenth Surface

K=−0.92674

A4=−1.83059E-05

A6=−3.30349E-08

A8=−2.28321E-09

A10=−6.15846E-13

Nineteenth Surface

K=0

A4=3.19375E-05

A6=3.31577E-08

A8=−2.88956E-09

A10=0

The glass material of the lens of the third lens group is S-BSM71manufactured by OHARA Co., Ltd.

νd and θg, F of S-BSM71 are as follows according to the publishedcatalogue.

νd=53.02

θg, F=0.5547

The variable amount data is illustrated in Table 5.

TABLE 5 FOCAL LENGTH 16.14591 29.48378 53.84341 VARIABLE A 0.479818.94913 23.54063 VARIABLE B 3.46925 3.31521 4.34035 VARIABLE C 18.753068.22939 2.59987 VARIABLE D 6.13180 2.96958 1.64988 VARIABLE E 27.3505439.92413 52.30469

FIGS. 18, 19, 20 are the aberration diagrams at the wide-angle end,intermediate distance, telephoto end in Embodiment 5, respectively.

Embodiment 6

Embodiment 6 is a zoom lens illustrated in FIG. 21.

f = 16.146~53.852  F = 3.62~5.77  ω = 41.53~14.87 SURFACE NUMBER R D Ndνd 1 52.97005 1.31000 1.84666 23.78 2 35.71101 5.48584 1.77250 49.60 3189.65170 VARIABLE A 4 57.34337 0.95497 2.00100 29.13 5 11.09490 6.362896 −52.53144 0.80001 1.77030 47.40 7 36.40322 1.16039 8 30.42534 4.238291.84666 23.78 9 −30.42507 VARIABLE B 10 −22.85191 0.80000 1.64850 53.02(S-BSM71) 11 −92.38759 VARIABLE C 12 ∞ (APERTURE STOP) 1.40001 1319.49107 3.32058 1.51633 64.06 14 −25.78639 0.11538 15 18.99577 4.017331.51742 52.43 16 −18.99577 1.40000 1.83400 37.16 17 18.99577 VARIABLE D18 19.38104 5.59999 1.58913 61.15 19 −23.21203 0.10000 20 34.690370.80000 1.90366 31.32 21 14.67162 VARIABLE E 22 ∞ 0.70000 1.53770 66.6023 ∞ 1.50000 24 ∞ 0.70000 1.50000 64.00 25 ∞

The aspheric surface data is as follows.

Sixth Surface

K=0

A4=2.63554E-05

A6=−1.09237E-06

A8=9.8447E-09

A10=−3.41409E-11

Seventh Surface

K=0

A4=2.93738E-06

A6=−1.13624E-06

A8=1.01043E-08

A10=−3.88306E-11

Thirteenth Surface

K=0

A4=3.21402E-07

A6=−1.03872E-07

A8=6.34622E-09

A10=−1.99948E-10

Fourteenth Surface

K=0

A4=2.47699E-05

A6=−2.4115E-07

A8=9.50458E-09

A10=−2.36136E-10

Eighteenth Surface

K=−0.57855

A4=−1.83484E-05

A6=−2.90044E-08

A8=−1.90061E-09

A10=−5.50054E-12

Nineteenth Surface

K=−0.09961

A4=3.54974E-05

A6=3.43435E-08

A8=−3.14805E-09

The glass material of the lens of the third lens group is S-BSM71manufactured by OHARA Co., Ltd.

νd and θg, F of S-BSM71 are as follows according to the publishedcatalogue.

νd=53.02

θg, F=0.5547

The variable amount data is illustrated in Table 6.

TABLE 6 FOCAL LENGTH 16.14575 29.48616 53.85229 VARIABLE A 1.0000310.71413 26.85616 VARIABLE B 3.49515 3.27157 4.27495 VARIABLE C 18.580048.07056 2.49995 VARIABLE D 26.45879 3.30413 1.64995 VARIABLE E 26.4587938.93855 51.55163

FIGS. 22, 23, 24 are the aberration diagrams at the wide-angle end,intermediate distance, telephoto end in Embodiment 6, respectively.

Embodiment 7

Embodiment 7 is a zoom lens illustrated in FIG. 25.

f = 16.146~53.852  F = 3.61~5.76  ω = 41.53~14.87 SURFACE NUMBER R D Ndνd 1 53.02258 1.31000 1.84666 23.78 2 35.94362 5.46329 1.77250 49.60 3188.67998 VARIABLE A 4 54.87412 0.95512 2.00100 29.13 5 10.79646 6.445876 −51.91885 0.80000 1.74320 49.29 7 40.63394 1.06371 8 31.38598 4.082431.84666 23.78 9 −31.38598 VARIABLE B 10 −23.00149 0.80000 1.65160 58.55(S-LAL7) 11 −97.40089 VARIABLE C 12 ∞ (APERTURE STOP) 1.39999 1319.57334 3.29549 1.51633 64.06 14 −25.26589 0.10000 15 19.46405 3.890711.51742 52.43 16 −19.46405 1.40519 1.83400 37.16 17 19.46405 VARIABLE D18 19.69818 5.60000 1.58913 61.15 19 −22.10614 0.10000 20 38.973490.80019 1.90366 31.32 21 15.14672 VARIABLE E 22 ∞ 0.70000 1.53770 66.6023 ∞ 1.50000 24 ∞ 0.70000 1.50000 64.00 25 ∞

The aspheric surface data is as follows.

Sixth Surface

K=0

A4=3.46877E-05

A6=−1.27443E-06

A8=1.11921E-08

A10=−4.40045E-11

Seventh Surface

K=0

A4=6.8617E-06

A6=−1.34447E-06

A8=1.13537E-08

A10=−4.81564E-11

Thirteenth Surface

K=0

A4=−1.2513E-06

A6=−4.84014E-08

A8=5.40686E-09

A10=−2.0620E-10

Fourteenth Surface

K=0

A4=2.71708E-05

A6=−2.3373E-07

A8=9.93932E-09

A10=−2.54318E-10

Eighteenth Surface

K=−0.65075

A4=−1.90482E-05

A6=−3.34777E-08

A8=−1.71693E-09

A10=−5.56274E-12

Nineteenth Surface

K=−0.20854

A4=3.63343E-05

A6=2.45318E-08

A8=−2.95008E-09

The glass material of the lens of the third lens group is S-LAL7manufactured by OHARA Co., Ltd.

νd and θg, F of S-LAL7 are as follows according to the publishedcatalogue.

νd=58.55

θg, F=0.5425

The variable amount data is illustrated in Table 7.

TABLE 7 FOCAL LENGTH 16.14586 29.48668 53.85211 VARIABLE A 1.0000310.81399 27.00555 VARIABLE B 3.56892 3.23901 4.21342 VARIABLE C 18.199447.95884 2.50002 VARIABLE D 7.23212 3.33550 1.65001 VARIABLE E 26.7650339.32439 52.06792

FIGS. 26, 27, 28 are the aberration diagrams at the wide-angle end,intermediate distance, telephoto end in Embodiment 7, respectively.

Embodiment 8

Embodiment 8 is a zoom lens illustrated in FIG. 29.

f = 16.145~53.86  F = 3.64~5.75  ω = 41.53~15.0 SURFACE NUMBER R D Nd νd1 51.57017 1.35033 1.84666 23.78 2 35.08789 5.69112 1.7725 49.6 3182.91872 VARIABLE A 4 44.57654 0.98972 2.001 29.13 5 10.55643 6.75921 6−44.69477 0.80002 1.7432 49.29 7 47.5051 1.35366 8 32.75877 3.829771.84666 23.78 9 −32.75877 VARIABLE B 10 −24.76086 0.8   1.6516 58.55(S-LAL7) 11 −153.4119 VARIABLE C 12 ∞ 1.40078 13 18.96748 3.752451.51633 64.06 14 −24.25341 0.09999 15 18.77954 4.04255 1.51742 52.43 16−18.77954 1.3999 1.834 37.16 17 18.77954 VARIABLE D 18 22.71409 5.000331.58913 61.15 19 −20.0266 0.10002 20 56.47649 0.79994 1.90366 31.32 2117.45296 VARIABLE E 22 ∞ 0.70000 1.53770 66.60 23 ∞ 1.50000 24 ∞ 0.700001.50000 64.00 25 ∞

The aspheric surface data is as follows.

Sixth Surface

K=0.000000E+00

A4=2.855640E-05

A6=−1.210950E-06

A8=1.113490E-08

A10=−5.459440E-11

Seventh Surface

K=0.000000E+00

A4=1.969800E-06

A6=−1.114090E-06

A8=8.666190E-09

A10=−3.951870E-11

Thirteenth Surface

K=0.000000E+00

A4=−4.439230E-06

A6=−9.177670E-08

A8=4.021770E-09

A10=−1.681980E-10

Fourteenth Surface

K=0.000000E+00

A4=2.834640E-05

A6=−2.280050E-07

A8=6.993710E-09

A10=−2.005280E-10

Eighteenth Surface

K=−4.551530E-01

A4=−2.952530E-05

A6=2.344050E-08

A8=−4.179360E-09

A10=2.547520E-12

Nineteenth Surface

K=−6.679000E-01

A4=2.331810E-05

A6=4.120810E-08

A8=−4.205110E-09

The glass material of the lens of the third lens group is S-LAL7manufactured by OHARA Co., Ltd.

νd and θg, F of S-LAL7 are as follows according to the publishedcatalogue.

νd=58.55

θg, F=0.5425

The variable amount data is illustrated in Table 8.

TABLE 8 FOCAL LENGTH 16.15 29.48 53.86 VARIABLE A 0.50072 10.0820226.42607 VARIABLE B 3.48321 3.16098 4.17288 VARIABLE C 17.98655 7.895562.50075 VARIABLE D 5.94076 2.88738 1.65198 VARIABLE E 26.7382 39.3260451.63359

FIGS. 30, 31, 32 are the aberration diagrams at the wide-angle end,intermediate distance, telephoto end in Embodiment 8, respectively.

The parameter values of conditions in respective embodiments areillustrated in Table 9.

TABLE 9 EMBODI- EMBODI- EMBODI- EMBODI- EMBODI- EMBODI- EMBODI- EMBODI-MENT 1 MENT 2 MENT 3 MENT 4 MENT 5 MENT 6 MENT 7 MENT 8 CONDITION (1)2.39 3.40 5.60 1.67 4.11 4.82 5.23 9.17 CONDITION (2) 2.43 3.42 5.671.69 4.15 4.86 5.26 9.22 CONDITION (3) 1.93 1.85 1.68 2.25 1.59 1.6 1.571.54 CONDITION (4) 65.44 65.44 53.02 65.44 53.02 53.02 58.55 58.55CONDITION (5) 0.89 0.89 0.89 0.88 0.89 0.89 0.89 0.89 CONDITION (6) 3.343.34 3.34 2.83 3.33 3.34 3.34 3.34

As illustrated in FIG. 9, Embodiments 1-8 satisfy the conditions(1)-(6).

The aberration is preferably corrected and a preferable performance isobtained in each embodiment.

In the zoom lens in each of Embodiments 1-7, the parameter values of theabove conditions (7)-(12) are within the ranges of the conditions,respectively.

Next, an embodiment of a digital camera as an imaging device in whichthe zoom lens according to each of the above Embodiments 1-7 is adoptedas an optical system for photographing will be described with referenceto FIGS. 34-37. FIG. 36 is a perspective view schematically illustratingan external appearance of a digital camera as seen from the front side,which is the object side, namely, the subject side. FIG. 37 is aperspective view schematically illustrating the external appearance ofthe digital camera as seen from the back side, which is thephotographer's side. FIG. 34 is a block diagram schematicallyillustrating the functional constitution of the digital camera. Inaddition, the imaging device is described with an example of a digitalcamera. However, the zoom lens of the present invention can be appliedto a silver salt film camera using a silver salt film as a conventionalimage-recording medium. An information device, for example, a portabledigital assistant (PDA) or a cell phone having a camera function iswidely used. Such an information device differs in an externalappearance, but has functions and constitutions substantially similar tothose in a digital camera. The zoom lens of the present invention can beapplied to such an information device as an optical system forphotographing.

As illustrated in FIGS. 36, 37, the digital camera includes aphotographing lens 101, optical finder 102, strobe (flash light) 103,shutter button 104, camera body 105, power source switch 106, liquidcrystal monitor 107, operation button 108, memory card socket 109 andzoom switch 110. As illustrated in FIG. 34, the digital camera includesa central processing unit (CPU) 111, image processor 112,light-receiving element 113, signal processor 114, semiconductor memory115 and communication card 116.

The digital camera includes the photographing lens 101 as an opticalsystem for photographing and the light-receiving element 113 constitutedas an image sensor using a CMOS (complementary metal-oxidesemiconductor) or CCD (charged coupled device), and is configured toread a subject optical image formed by the photographing lens 101 withthe light-receiving element 113. The zoom lens described in each ofEmbodiments 1-7 is used as the photographing lens 101.

The output of the light-receiving element 113 is processed by the signalprocessor 114 which is controlled by the central processing unit 111,and is converted into digital image information. Such a digital cameraincludes a unit which converts an image (subject image) into digitalimage information. This unit is constituted by the light-receivingelement 113, signal processor 114, central processing unit (CPU) 111which controls these, and the like.

After a predetermined image process is applied to the image informationdigitized by the signal processor 114 in the image processor 112 whichis controlled by the central processing unit 111, the image informationis recorded in the semiconductor memory 115 such as a non-volatilememory. In this case, the semiconductor memory 115 can be a memory cardprovided in the memory card socket 109, or can be a semiconductor memorybuilt in a camera body (on-board). The liquid crystal monitor 107 candisplay an image in photographing or can display an image recorded inthe semiconductor memory 115. The image recorded in the semiconductormemory 115 can be sent outside through, for example, a communicationcard 116 provided in a not shown communication socket.

The object surface of the photographing lens 101 is covered by a notshown lens barrier when a camera is carried. If a user turns on thepower by the operation of the power source switch 106, the lens barrieropens and the object surface is exposed. In this case, the opticalsystem of each group constituting the zoom lens in the lens barrel ofthe photographing lens 101 is arranged at the short focal point end(wide-angle end), for example. By operating the zoom switch 110, thearrangement of the optical system of each group is changed, and amagnification can be changed to the long focal point end (telephoto end)through the intermediate focal length. In addition, it is preferable forthe optical system of the optical finder 102 to change a magnificationin accordance with the change in the field angle of the photographinglens 101.

In many cases, the focusing is performed by the half-pressing operationof the shutter button 104. The focusing lens in the zoom lensillustrated in each of Embodiments 1-7 can be operated by the movementof a part of the lens groups constituting the zoom lens or the movementof the light-receiving element. The photographing is performed by thefull-pressing operation of the shutter button 104. After that, the abovedescribed processes are conducted.

When displaying an image recorded in the semiconductor memory 115 on theliquid crystal monitor 107, or sending the image outside via thecommunication card 116 or the like, the operation button 108 is operatedas defined. The semiconductor memory 115, communication card 116 and thelike are provided in dedicated or general-purposed sockets such as thememory card socket 109 and communication card socket.

The photographing lens 101 constituted by using the zoom lensillustrated in each of Embodiments 1-7 can be used in theabove-described digital camera (imaging device) or information device asan optical system for photographing. Accordingly, a small and highquality digital camera (imaging device) or information device using alight-receiving element having 10-15 million pixels can be accomplished.

Such a zoom lens can be applied to a zoom photographing lens of a silversalt camera or a projection lens of a projector.

As described above, a small zoom lens having a compact focusing group,small displacement in focusing and a high AF speed can be achieved bythe above constitution.

Moreover, a zoom lens having a half-field angle at the wide-angle end of36.8° or more, a magnification ratio of about 2.8 to 5 times,well-corrected aberrations and a resolution corresponding to a small andhigh resolution imaging element can be achieved as described in theabove embodiments.

By providing such a zoom lens, a small and high performance imagingdevice can be achieved.

According to the embodiments of the present invention, a zoom lenshaving a compact focusing lens group, small displacement of the focusinglens group, reduced power for movement, well corrected aberrations and alight-receiving element having over 10 million pixels can be provided.

An imaging device and information device having a photographing functionsuch as a compact and high performance digital camera can be alsoprovided by using such a zoom lens.

Although the embodiments of the present invention have been describedabove, the present invention is not limited thereto. It should beappreciated that variations may be made in the embodiments described bypersons skilled in the art without departing from the scope of thepresent invention.

What is claimed is:
 1. A zoom lens comprising, in order from an objectside in an optical axis: a first lens group having a positive refractivepower; a second lens group having a negative refractive power; a thirdlens group having a negative refractive power; a fourth lens grouphaving a positive refractive power; a fifth lens group having a positiverefractive power; and an aperture stop arranged between the third lensgroup and the fourth lens group, an interval between the first lensgroup and the second lens group being increased, an interval between thesecond lens group and the third lens group being increased, an intervalbetween the third lens group and the fourth lens group being decreased,and an interval between the fourth lens group and the fifth lens groupbeing decreased when changing a magnification from a wide-angle end to atelephoto end, the third lens group including one negative lens made ofa negative meniscus lens having a concave surface on the object side,and focusing being performed by moving the third lens group in anoptical axis direction, wherein a curvature radius of an object sidesurface of the third lens group, R31, a curvature radius of an imageside surface of the third lens group, R32, a focal length of the thirdlens group, F3, a synthesis focal length of the second and third lensgroups at the wide-angle end, F23w, a synthesis focal length of thesecond and third lens groups at the telephoto end, F23t, a focal lengthat the wide-angle end, Fw, a focal length at the telephoto end, Ft, and√(Fw×Ft), Fm satisfy the following conditions (1), (2), (3):1.0<(R31−R32)/|F23w|<10.0  (1)1.0<(R31−R32)/|F23t|<10.0  (2)1.4<|F3|/Fm<2.5  (3).
 2. The zoom lens according to claim 1, wherein amaximum image height, Y′ and the focal length at the wide-angle end, Fwsatisfy the following condition (5):0.75<Y′/Fw  (5).
 3. The zoom lens according to claim 1, wherein thefocal length at the telephoto end, Ft and the focal length of thewide-angle end, Fw satisfy the following condition (6):2.8<Ft/Fw  (6).
 4. The zoom lens according to claim 1, wherein an Abbe'snumber of a material of one negative lens constituting the third lensgroup, νd satisfies the following condition (4):νd>50  (4).
 5. An information device including a photographing functioncomprising the zoom lens according to claim 1 as an optical system forphotographing.
 6. The information device according to claim 5, whereinan object image by the zoom lens is formed on a light-receiving surfaceof an imaging element.
 7. The information device according to claim 6comprising a portable digital assistant.